Peripheral and central vascular access devices are a fundamental and essential part of healthcare delivery, used extensively in hospital and community settings to meet the challenging and complex IV therapy requirements of the modern-day patient. For vascular access devices (VAD) to be a safe and effective tool for the administration of IV therapy, they must be reliable. Reliability in this context refers to optimal catheter function, demonstrated by the ease of flushing and aspirating, combined with an absence of associated complications. Proficient care and maintenance of these devices by healthcare professionals requires a high degree of knowledge, skill and understanding. In this section, we explore the details of flushing by examining how, why, when and with what solution vascular devices are to be flushed.